Tag Archives: Crop Yields

April 16th, 2014, by Tim Radford

FOR IMMEDIATE RELEASEThere may be a higher price for our descendants to pay for the greenhouse gas build-up, researchers say, as the real costs are updated.

LONDON, 16 April – Economists and scientists may have seriously underestimated the “social cost” of carbon emissions to future generations, according to a warning in Nature.

Social cost is a calculation in US dollars of the future damage that might be done by the emission of one metric ton of carbon dioxide as greenhouse gas levels soar and climates change, sea levels rise and temperature records are broken in future decades.

How much would society save if it didn’t emit that tonne of CO2? One recent US estimate is $37. Such a measure helps civil servants, businessmen and ministers to calculate the impact of steps that might be taken.

On the other hand, say Richard Revesz of New York University School of Law and US and Swedish colleagues, assumptions of cost per tonne – and these range from $12 to $64 according to various calculations – are based on models that need to be improved and extended. The cost of climate change could be higher, for four reasons.

Flawed assumptions

The impact of historic temperature variation suggests societies and economies may be more vulnerable than the models predict, and in this case weather variability is more important than average weather – because crop yields are vulnerable to extremes of temperature.

Then the models omit the damage to productivity, and to the value of capital stock, because of lower growth rates: as these lower growth rates compound each other, human welfare will begin to decline. And that’s without factoring in climate-induced wars, coups or societal collapse.

Third, the models assume that the value people attach to ecosystems (and water is an ecosystem service) remains constant. But, they point out, as commodities become scarce, value increases, so the costs of ecosystem damage will rise faster than models predict.

Finally, the models assume that a constant discount rate can translate future harms into today’s dollars. But discount rates of the future may not be constant.

More warming

“What now?” they ask. “Modellers, scientists and environmental economists must continue to step outside their silos and work together to identify research gaps and modelling limitations.”

They hint at an even deeper problem: the basis of the social harm costs dates from calculations more than 20 years old, and is predicated on an average global warming of less than 3°C. Yet without mitigation, the Intergovernmental Panel on Climate Change projects a warming of 4°C by the end of the century.

“If warming continues unchecked into the twenty-second century, it could render parts of the planet effectively uninhabitable during the hottest days of summer, with consequences that would be challenging to monetize,” they write.

Economic harm may not be the only thing underestimated. Michael Mann, a meteorologist at Penn State University in the US, reports in Geophysical Research Letters that the so-called “slowdown” in global warming during this decade could be because of an underestimate of the impact of a meteorological monster called the Atlantic Multidecadal Oscillation (AMO), an oceanographic cycle of warming and cooling that delivers natural change in northern hemisphere weather patterns.

More methane

A misreading of this cycle – probably because scientists have not known about it for long – could account for this apparent slowdown. “Some researchers in the past attributed a portion of Northern Hemispheric warming to a warm phase of the AMO,” said Professor Mann.

“The true AMO signal, instead, appears likely to have been in a cooling phase in recent decades, offsetting some of the anthropogenic warming temporarily.” And when the rate of warming rises again, there’s yet more alarming evidence of possible acceleration, according to new research.

The thawing of the Arctic sea ice is also accompanied by a softening and warming of the Arctic permafrost, and changes in the chemistry of the preserved peat, that could release ever larger amounts of methane. Methane is a greenhouse gas, present in smaller quantities than carbon dioxide, but 34 times more potent as a warming agent over 100 years.

“The world is getting warmer, and the additional release of gas would only add to our problems,” said Jeff Chanton of Florida State University, a co-author. – Climate News Network

FOR IMMEDIATE RELEASEThere may be a higher price for our descendants to pay for the greenhouse gas build-up, researchers say, as the real costs are updated.

LONDON, 16 April – Economists and scientists may have seriously underestimated the “social cost” of carbon emissions to future generations, according to a warning in Nature.

Social cost is a calculation in US dollars of the future damage that might be done by the emission of one metric ton of carbon dioxide as greenhouse gas levels soar and climates change, sea levels rise and temperature records are broken in future decades.

How much would society save if it didn’t emit that tonne of CO2? One recent US estimate is $37. Such a measure helps civil servants, businessmen and ministers to calculate the impact of steps that might be taken.

On the other hand, say Richard Revesz of New York University School of Law and US and Swedish colleagues, assumptions of cost per tonne – and these range from $12 to $64 according to various calculations – are based on models that need to be improved and extended. The cost of climate change could be higher, for four reasons.

Flawed assumptions

The impact of historic temperature variation suggests societies and economies may be more vulnerable than the models predict, and in this case weather variability is more important than average weather – because crop yields are vulnerable to extremes of temperature.

Then the models omit the damage to productivity, and to the value of capital stock, because of lower growth rates: as these lower growth rates compound each other, human welfare will begin to decline. And that’s without factoring in climate-induced wars, coups or societal collapse.

Third, the models assume that the value people attach to ecosystems (and water is an ecosystem service) remains constant. But, they point out, as commodities become scarce, value increases, so the costs of ecosystem damage will rise faster than models predict.

Finally, the models assume that a constant discount rate can translate future harms into today’s dollars. But discount rates of the future may not be constant.

More warming

“What now?” they ask. “Modellers, scientists and environmental economists must continue to step outside their silos and work together to identify research gaps and modelling limitations.”

They hint at an even deeper problem: the basis of the social harm costs dates from calculations more than 20 years old, and is predicated on an average global warming of less than 3°C. Yet without mitigation, the Intergovernmental Panel on Climate Change projects a warming of 4°C by the end of the century.

“If warming continues unchecked into the twenty-second century, it could render parts of the planet effectively uninhabitable during the hottest days of summer, with consequences that would be challenging to monetize,” they write.

Economic harm may not be the only thing underestimated. Michael Mann, a meteorologist at Penn State University in the US, reports in Geophysical Research Letters that the so-called “slowdown” in global warming during this decade could be because of an underestimate of the impact of a meteorological monster called the Atlantic Multidecadal Oscillation (AMO), an oceanographic cycle of warming and cooling that delivers natural change in northern hemisphere weather patterns.

More methane

A misreading of this cycle – probably because scientists have not known about it for long – could account for this apparent slowdown. “Some researchers in the past attributed a portion of Northern Hemispheric warming to a warm phase of the AMO,” said Professor Mann.

“The true AMO signal, instead, appears likely to have been in a cooling phase in recent decades, offsetting some of the anthropogenic warming temporarily.” And when the rate of warming rises again, there’s yet more alarming evidence of possible acceleration, according to new research.

The thawing of the Arctic sea ice is also accompanied by a softening and warming of the Arctic permafrost, and changes in the chemistry of the preserved peat, that could release ever larger amounts of methane. Methane is a greenhouse gas, present in smaller quantities than carbon dioxide, but 34 times more potent as a warming agent over 100 years.

April 16th, 2014, by Tim Radford

FOR IMMEDIATE RELEASEThere may be a higher price for our descendants to pay for the greenhouse gas build-up, researchers say, as the real costs are updated.LONDON, 16 April – Economists and scientists may have seriously underestimated the “social cost” of carbon emissions to future generations, according to a warning in Nature. Social cost is a calculation in US dollars of the future damage that might be done by the emission of one metric ton of carbon dioxide as greenhouse gas levels soar and climates change, sea levels rise and temperature records are broken in future decades. How much would society save if it didn’t emit that tonne of CO2? One recent US estimate is $37. Such a measure helps civil servants, businessmen and ministers to calculate the impact of steps that might be taken. On the other hand, say Richard Revesz of New York University School of Law and US and Swedish colleagues, assumptions of cost per tonne – and these range from $12 to $64 according to various calculations – are based on models that need to be improved and extended. The cost of climate change could be higher, for four reasons.

Flawed assumptions

The impact of historic temperature variation suggests societies and economies may be more vulnerable than the models predict, and in this case weather variability is more important than average weather – because crop yields are vulnerable to extremes of temperature. Then the models omit the damage to productivity, and to the value of capital stock, because of lower growth rates: as these lower growth rates compound each other, human welfare will begin to decline. And that’s without factoring in climate-induced wars, coups or societal collapse. Third, the models assume that the value people attach to ecosystems (and water is an ecosystem service) remains constant. But, they point out, as commodities become scarce, value increases, so the costs of ecosystem damage will rise faster than models predict. Finally, the models assume that a constant discount rate can translate future harms into today’s dollars. But discount rates of the future may not be constant.

More warming

“What now?” they ask. “Modellers, scientists and environmental economists must continue to step outside their silos and work together to identify research gaps and modelling limitations.” They hint at an even deeper problem: the basis of the social harm costs dates from calculations more than 20 years old, and is predicated on an average global warming of less than 3°C. Yet without mitigation, the Intergovernmental Panel on Climate Change projects a warming of 4°C by the end of the century. “If warming continues unchecked into the twenty-second century, it could render parts of the planet effectively uninhabitable during the hottest days of summer, with consequences that would be challenging to monetize,” they write. Economic harm may not be the only thing underestimated. Michael Mann, a meteorologist at Penn State University in the US, reports in Geophysical Research Letters that the so-called “slowdown” in global warming during this decade could be because of an underestimate of the impact of a meteorological monster called the Atlantic Multidecadal Oscillation (AMO), an oceanographic cycle of warming and cooling that delivers natural change in northern hemisphere weather patterns.

More methane

A misreading of this cycle – probably because scientists have not known about it for long – could account for this apparent slowdown. “Some researchers in the past attributed a portion of Northern Hemispheric warming to a warm phase of the AMO,” said Professor Mann. “The true AMO signal, instead, appears likely to have been in a cooling phase in recent decades, offsetting some of the anthropogenic warming temporarily.” And when the rate of warming rises again, there’s yet more alarming evidence of possible acceleration, according to new research. The thawing of the Arctic sea ice is also accompanied by a softening and warming of the Arctic permafrost, and changes in the chemistry of the preserved peat, that could release ever larger amounts of methane. Methane is a greenhouse gas, present in smaller quantities than carbon dioxide, but 34 times more potent as a warming agent over 100 years. If the permafrost melts entirely, that would put five times the present levels of carbon into the atmosphere, US researchers report in the journal Proceedings of the National Academy of Sciences. “The world is getting warmer, and the additional release of gas would only add to our problems,” said Jeff Chanton of Florida State University, a co-author. – Climate News Network

FOR IMMEDIATE RELEASEThere may be a higher price for our descendants to pay for the greenhouse gas build-up, researchers say, as the real costs are updated.LONDON, 16 April – Economists and scientists may have seriously underestimated the “social cost” of carbon emissions to future generations, according to a warning in Nature. Social cost is a calculation in US dollars of the future damage that might be done by the emission of one metric ton of carbon dioxide as greenhouse gas levels soar and climates change, sea levels rise and temperature records are broken in future decades. How much would society save if it didn’t emit that tonne of CO2? One recent US estimate is $37. Such a measure helps civil servants, businessmen and ministers to calculate the impact of steps that might be taken. On the other hand, say Richard Revesz of New York University School of Law and US and Swedish colleagues, assumptions of cost per tonne – and these range from $12 to $64 according to various calculations – are based on models that need to be improved and extended. The cost of climate change could be higher, for four reasons.

Flawed assumptions

The impact of historic temperature variation suggests societies and economies may be more vulnerable than the models predict, and in this case weather variability is more important than average weather – because crop yields are vulnerable to extremes of temperature. Then the models omit the damage to productivity, and to the value of capital stock, because of lower growth rates: as these lower growth rates compound each other, human welfare will begin to decline. And that’s without factoring in climate-induced wars, coups or societal collapse. Third, the models assume that the value people attach to ecosystems (and water is an ecosystem service) remains constant. But, they point out, as commodities become scarce, value increases, so the costs of ecosystem damage will rise faster than models predict. Finally, the models assume that a constant discount rate can translate future harms into today’s dollars. But discount rates of the future may not be constant.

More warming

“What now?” they ask. “Modellers, scientists and environmental economists must continue to step outside their silos and work together to identify research gaps and modelling limitations.” They hint at an even deeper problem: the basis of the social harm costs dates from calculations more than 20 years old, and is predicated on an average global warming of less than 3°C. Yet without mitigation, the Intergovernmental Panel on Climate Change projects a warming of 4°C by the end of the century. “If warming continues unchecked into the twenty-second century, it could render parts of the planet effectively uninhabitable during the hottest days of summer, with consequences that would be challenging to monetize,” they write. Economic harm may not be the only thing underestimated. Michael Mann, a meteorologist at Penn State University in the US, reports in Geophysical Research Letters that the so-called “slowdown” in global warming during this decade could be because of an underestimate of the impact of a meteorological monster called the Atlantic Multidecadal Oscillation (AMO), an oceanographic cycle of warming and cooling that delivers natural change in northern hemisphere weather patterns.

More methane

A misreading of this cycle – probably because scientists have not known about it for long – could account for this apparent slowdown. “Some researchers in the past attributed a portion of Northern Hemispheric warming to a warm phase of the AMO,” said Professor Mann. “The true AMO signal, instead, appears likely to have been in a cooling phase in recent decades, offsetting some of the anthropogenic warming temporarily.” And when the rate of warming rises again, there’s yet more alarming evidence of possible acceleration, according to new research. The thawing of the Arctic sea ice is also accompanied by a softening and warming of the Arctic permafrost, and changes in the chemistry of the preserved peat, that could release ever larger amounts of methane. Methane is a greenhouse gas, present in smaller quantities than carbon dioxide, but 34 times more potent as a warming agent over 100 years. If the permafrost melts entirely, that would put five times the present levels of carbon into the atmosphere, US researchers report in the journal Proceedings of the National Academy of Sciences. “The world is getting warmer, and the additional release of gas would only add to our problems,” said Jeff Chanton of Florida State University, a co-author. – Climate News Network

March 21st, 2014, by Tim Radford

FOR IMMEDIATE RELEASEYields of several major crops are likely to be seriously affected by rising temperatures, scientists say, with spells of extreme heat posing the greatest risk.LONDON, 21 March – Rampant climate change driven by ever-rising levels of carbon dioxide in the atmosphere poses a serious threat to world food supply, according to a new study in Environmental Research Letters. The hazard comes not from high average temperatures, but the likelihood of heat extremes at times when crops are most sensitive to stress. And the message is: those communities that rely on maize as a staple are more at risk than most. Delphine Deryng of the Tyndall Centre for Climate Change Research at the University of East Anglia in the UK and colleagues looked at one of the big puzzles of the coming decades: what will global warming do for crop yields? It is not a simple question: climate change must mean more evaporation, more precipitation, longer growing seasons, more warmth, and higher levels of the carbon dioxide that plants exploit by photosynthesis (the process they use to convert light into chemical energy), so the consequence ought to be greater yields. But as every farmer knows, what matters most is the timing of all that warmth, rain, and those dry spells in which the harvest can ripen.

Danger in extremes

There is a second consideration. Climate is the sum of all events. Rather than a steady overall rise in daily temperatures, an increasing number of ever-larger regions are predicted to experience ever more intense extremes of heat, and sometimes cold. Plants can be very sensitive to extremes of heat at flowering time: if the thermometer goes up, the pollen becomes increasingly sterile and less seed is likely to be set. So an extended heat wave in the wrong season could be calamitous. The Tyndall team included the assumption that nothing would be done about climate change – that is, that governments, industry and people would continue with a business-as-usual scenario. They then chose three well-studied and vital crops – spring wheat, maize and soybean – and tested predictions under 72 different climate change scenarios for the rest of this century. They allowed for the already-established benign effects of carbon dioxide-driven warming, one of which is that plants can make more tissue and at the same time use water more efficiently, and therefore respond more effectively to drought conditions. They also looked for the outcomes in places where yields could be most vulnerable: for example, the North American corn belt.

Emissions cuts essential

What they found was that – if carbon dioxide fertilisation effects are not taken into account – then maize, wheat and soya yields are all likely to fall, in all five top-producing countries for each of these crops. When they factored in the benefits of more CO2 in the atmosphere, the picture changed. There would be positive impacts on soya and wheat, but not on maize. There is another proviso: so far, the benefits of extra CO2 have been confirmed in experimental plant laboratories. The experience in the fields 60 years in the future may be rather different. And in any case, these positive impacts could be severely offset by extremes of heat at the moment when the crops were most vulnerable, so overall, harvests remain at risk. The best answer, the scientists argue, is to attempt to limit climate change. “Climate mitigation policy would help reduce risks of serious negative impacts on maize worldwide and reduce risks of extreme heat stress that threaten global crop production,” says Deryng. – Climate News Network

FOR IMMEDIATE RELEASEYields of several major crops are likely to be seriously affected by rising temperatures, scientists say, with spells of extreme heat posing the greatest risk.LONDON, 21 March – Rampant climate change driven by ever-rising levels of carbon dioxide in the atmosphere poses a serious threat to world food supply, according to a new study in Environmental Research Letters. The hazard comes not from high average temperatures, but the likelihood of heat extremes at times when crops are most sensitive to stress. And the message is: those communities that rely on maize as a staple are more at risk than most. Delphine Deryng of the Tyndall Centre for Climate Change Research at the University of East Anglia in the UK and colleagues looked at one of the big puzzles of the coming decades: what will global warming do for crop yields? It is not a simple question: climate change must mean more evaporation, more precipitation, longer growing seasons, more warmth, and higher levels of the carbon dioxide that plants exploit by photosynthesis (the process they use to convert light into chemical energy), so the consequence ought to be greater yields. But as every farmer knows, what matters most is the timing of all that warmth, rain, and those dry spells in which the harvest can ripen.

Danger in extremes

There is a second consideration. Climate is the sum of all events. Rather than a steady overall rise in daily temperatures, an increasing number of ever-larger regions are predicted to experience ever more intense extremes of heat, and sometimes cold. Plants can be very sensitive to extremes of heat at flowering time: if the thermometer goes up, the pollen becomes increasingly sterile and less seed is likely to be set. So an extended heat wave in the wrong season could be calamitous. The Tyndall team included the assumption that nothing would be done about climate change – that is, that governments, industry and people would continue with a business-as-usual scenario. They then chose three well-studied and vital crops – spring wheat, maize and soybean – and tested predictions under 72 different climate change scenarios for the rest of this century. They allowed for the already-established benign effects of carbon dioxide-driven warming, one of which is that plants can make more tissue and at the same time use water more efficiently, and therefore respond more effectively to drought conditions. They also looked for the outcomes in places where yields could be most vulnerable: for example, the North American corn belt.

Emissions cuts essential

What they found was that – if carbon dioxide fertilisation effects are not taken into account – then maize, wheat and soya yields are all likely to fall, in all five top-producing countries for each of these crops. When they factored in the benefits of more CO2 in the atmosphere, the picture changed. There would be positive impacts on soya and wheat, but not on maize. There is another proviso: so far, the benefits of extra CO2 have been confirmed in experimental plant laboratories. The experience in the fields 60 years in the future may be rather different. And in any case, these positive impacts could be severely offset by extremes of heat at the moment when the crops were most vulnerable, so overall, harvests remain at risk. The best answer, the scientists argue, is to attempt to limit climate change. “Climate mitigation policy would help reduce risks of serious negative impacts on maize worldwide and reduce risks of extreme heat stress that threaten global crop production,” says Deryng. – Climate News Network

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